The present invention relates to method and apparatus for forming a wheel in a manner which overcomes difficulties which the prior art has had with fatigue failures of the web and its attachment to the rim.
When prior art wheels have been run with overloads to induce failure, fatigue cracks have usually occurred in the center of the web where it is attached to its supporting axle. When the wheels have been fabricated utilizing welding, failures have also occured in the welds which have attached the rim to the web. The failures in these areas of the wheel have been so apparent to the industry, that an axiom has developed in the automotive industry that you do not machine or diminish the thickness of the web, since it is the "weakest link in the chain". On the other hand, the art has been reticent about using reinforcing plates for the web, not only because of their expense, but because of the weight which they would add to the rotating mass which must be accelerated and decelerated during the starting and stopping of the vehicle. Furthermore, in the interest of fuel economy, the industry is making great efforts to reduce the weight of automobiles, and any weight added to a wheel not only adds to the total weight of the vehicle, but more importantly, adds to the rotating mass which must be started and stopped.
On the other hand, everyone recognizes that wheels are critical to the safety of an automotive vehicle. What makes the problem of wheel design even more difficult is that the analysis of stresses in the metal of the wheel is complicated by many factors which seemingly defy accurate appraisal including tire unbalances, radial eccentricities of the rims which in turn support the tires, tolerances that are necessary for economical manufacture, and stresses that are created by the manufacturing processes used in forming the wheels. In the light of all these variables, and the inability to accurately calculate or predict the stresses involved; the problem of how best to form a wheel in a commercially feasible manufacturing process, and at a cost which the average consumer can afford, has continued since the start of the automotive industry.
In the light of this background, it is a principle object of the present invention to provide a new and improved method of manufacturing a wheel which overcomes problems of fatigue failures in the web and in its attachment to the rim.
Another object of the present invention is the provision of a new and improved apparatus for automatically carrying out the method of the present invention.
A further object of the present invention is the provision of new and improved wheels whose design overcomes stresses produced by alignment and bolting problems.
Further objects and advantages of the present invention will become apparent to those skilled in the art to which the invention relates from the following description of the preferred embodiments.